1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <boost/functional/hash.hpp>
#include <boost/optional.hpp>
#include <climits>
#include <cstdint>
#include <fmt/format.h>
#include <ostream>
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/bson/util/builder.h"
#include "mongo/util/bufreader.h"
#include "mongo/util/hex.h"
namespace mongo {
/**
* The key that uniquely identifies a Record in a Collection or RecordStore.
*/
class RecordId {
public:
// This set of constants define the boundaries of the 'normal' id ranges for the int64_t format.
static constexpr int64_t kMinRepr = LLONG_MIN;
static constexpr int64_t kMaxRepr = LLONG_MAX;
/**
* A RecordId that compares less than all int64_t RecordIds that represent documents in a
* collection.
*/
static RecordId minLong() {
return RecordId(kMinRepr);
}
/**
* A RecordId that compares greater than all int64_t RecordIds that represent documents in a
* collection.
*/
static RecordId maxLong() {
return RecordId(kMaxRepr);
}
RecordId() {
_buffer[kBufEnd] = Format::kNull;
}
/**
* Construct a RecordId that holds an int64_t. The raw value for RecordStore storage may be
* retrieved using getLong().
*/
explicit RecordId(int64_t s) {
memcpy(_buffer, &s, sizeof(s));
_buffer[kBufEnd] = Format::kLong;
}
/**
* Construct a RecordId that holds a small binary string. The raw value for RecordStore storage
* may be retrieved using getStr().
*/
explicit RecordId(const char* str, int32_t size) {
invariant(size > 0, "key size must be greater than 0");
// Must fit into the 16 byte buffer minus 1 byte for size and 1 format byte.
uassert(ErrorCodes::BadValue,
fmt::format("key size {} greater than maximum {}", size, kBufMaxSize - 2),
size + 2 <= kBufMaxSize);
_buffer[0] = static_cast<char>(size);
memcpy(_buffer + 1, str, size);
_buffer[kBufEnd] = Format::kSmallStr;
}
/**
* Construct a RecordId from two halves.
*/
RecordId(int high, int low) : RecordId((uint64_t(high) << 32) | uint32_t(low)) {}
/** Tag for dispatching on null values */
class Null {};
/**
* Helper to dispatch based on the underlying type. In most cases the RecordId type will be
* known in advance, but this may be used when the type is not known.
*/
template <typename OnNull, typename OnLong, typename OnStr>
auto withFormat(OnNull&& onNull, OnLong&& onLong, OnStr&& onStr) const {
switch (auto f = _format()) {
case Format::kNull:
return onNull(Null());
case Format::kLong:
return onLong(getLong());
case Format::kSmallStr: {
auto str = getStr();
return onStr(str.rawData(), str.size());
}
default:
MONGO_UNREACHABLE;
}
}
/**
* Returns the raw value to be used as a key in a RecordStore. Requires that this RecordId was
* constructed with a 64-bit integer value or null; invariants otherwise.
*/
int64_t getLong() const {
// In the the int64_t format, null can also be represented by '0'.
if (_format() == Format::kNull) {
return 0;
}
invariant(_format() == Format::kLong);
int64_t val;
memcpy(&val, _buffer, sizeof(val));
return val;
}
/**
* Returns the raw value to be used as a key in a RecordStore. Requires that this RecordId was
* constructed with a binary string value, and invariants otherwise.
*/
const StringData getStr() const {
invariant(_format() == Format::kSmallStr);
char size = _buffer[0];
invariant(size > 0);
invariant(size < kBufMaxSize - 1);
return StringData(_buffer + 1, size);
}
/**
* Returns true if this RecordId is not suitable for storage in a RecordStore.
*/
bool isNull() const {
// In the the int64_t format, null can also be represented by '0'.
if (_format() == Format::kLong) {
return getLong() == 0;
}
return _format() == Format::kNull;
}
/**
* Valid RecordIds are the only ones which may be used to represent Records. The range of valid
* RecordIds includes both "normal" ids that refer to user data, and "reserved" ids that are
* used internally. All RecordIds outside of the valid range are sentinel values.
*/
bool isValid() const {
return withFormat(
[](Null n) { return false; },
[&](int64_t rid) { return rid > 0; },
[&](const char* str, int size) { return size > 0 && size + 2 <= kBufMaxSize; });
}
/**
* Compares two RecordIds. Requires that both RecordIds are of the same format, unless one or
* both are null. Null always compares less than every other RecordId format.
*/
int compare(const RecordId& rhs) const {
if (_format() == Format::kNull && rhs._format() == Format::kNull) {
return 0;
} else if (_format() == Format::kNull) {
return -1;
} else if (rhs._format() == Format::kNull) {
return 1;
}
invariant(_format() == rhs._format());
return withFormat(
[](Null n) { return 0; },
[&](const int64_t rid) {
return rid == rhs.getLong() ? 0 : (rid > rhs.getLong()) ? 1 : -1;
},
[&](const char* str, int size) { return StringData(str, size).compare(rhs.getStr()); });
}
size_t hash() const {
size_t hash = 0;
withFormat([](Null n) {},
[&](int64_t rid) { boost::hash_combine(hash, rid); },
[&](const char* str, int size) {
boost::hash_combine(hash, std::string_view(str, size));
});
return hash;
}
std::string toString() const {
return withFormat(
[](Null n) { return std::string("null"); },
[](int64_t rid) { return std::to_string(rid); },
[](const char* str, int size) { return hexblob::encodeLower(str, size); });
}
/**
* Hash value for this RecordId. The hash implementation may be modified, and its behavior
* may differ across platforms. Hash values should not be persisted.
*/
struct Hasher {
size_t operator()(const RecordId& rid) const {
return rid.hash();
}
};
/**
* Formats this RecordId into a human-readable BSON object that may be passed around and
* deserialized with deserializeToken().
* Note: This is not to be used as a key to a RecordStore.
*/
void serializeToken(StringData fieldName, BSONObjBuilder* builder) const {
// Preserve the underlying format by using a different BSON type for each format.
withFormat([&](Null n) { builder->appendNull(fieldName); },
[&](int64_t rid) { builder->append(fieldName, rid); },
[&](const char* str, int size) {
builder->append(fieldName, hexblob::encodeLower(str, size));
});
}
/**
* Decode a token created by serializeToken().
*/
static RecordId deserializeToken(const BSONElement& elem) {
if (elem.isNull()) {
return RecordId();
} else if (elem.isNumber()) {
return RecordId(elem.numberLong());
} else if (elem.type() == BSONType::String) {
auto str = hexblob::decode(elem.String());
return RecordId(str.c_str(), str.size());
} else {
uasserted(ErrorCodes::BadValue,
fmt::format("Could not deserialize RecordId with type {}", elem.type()));
}
}
private:
enum { kBufEnd = 15, kBufMaxSize = 16 };
/**
* Specifies the storage format of this RecordId.
*/
enum Format : int8_t {
/** Contains no value */
kNull,
/** int64_t */
kLong,
/** variable-length binary string, up to 14 bytes */
kSmallStr
};
Format _format() const {
return static_cast<Format>(_buffer[kBufEnd]);
}
// Storage for this RecordId.
// - The last byte stores the Format.
// - For the kLong type, the first 8 bytes encode the value in machine-endian order.
// - For the kSmallStr type, the first byte encodes the length and the remaining bytes encode
// the string.
char _buffer[kBufMaxSize];
};
/**
* Enumerates all reserved ids that have been allocated for a specific purpose. These IDs may not be
* stored in RecordStores.
*/
enum class ReservationId { kWildcardMultikeyMetadataId };
/**
* Reservations tracks RecordId values that are reserved for specific usages and may not be stored
* in RecordStores.
*/
class RecordIdReservations {
public:
static constexpr int64_t kMinReservedLong = RecordId::kMaxRepr - (1024 * 1024);
/**
* Returns the reserved RecordId value for a given Reservation.
*/
static RecordId reservedIdFor(ReservationId res) {
// There is only one reservation at the moment.
invariant(res == ReservationId::kWildcardMultikeyMetadataId);
return RecordId(kMinReservedLong);
}
/**
* Returns true if this RecordId falls within the reserved range for a given RecordId type.
*/
static bool isReserved(RecordId id) {
if (id.isNull()) {
return false;
}
return id.getLong() >= kMinReservedLong && id.getLong() < RecordId::kMaxRepr;
}
};
inline bool operator==(RecordId lhs, RecordId rhs) {
return lhs.compare(rhs) == 0;
}
inline bool operator!=(RecordId lhs, RecordId rhs) {
return lhs.compare(rhs);
}
inline bool operator<(RecordId lhs, RecordId rhs) {
return lhs.compare(rhs) < 0;
}
inline bool operator<=(RecordId lhs, RecordId rhs) {
return lhs.compare(rhs) <= 0;
}
inline bool operator>(RecordId lhs, RecordId rhs) {
return lhs.compare(rhs) > 0;
}
inline bool operator>=(RecordId lhs, RecordId rhs) {
return lhs.compare(rhs) >= 0;
}
inline StringBuilder& operator<<(StringBuilder& stream, const RecordId& id) {
return stream << "RecordId(" << id.toString() << ')';
}
inline std::ostream& operator<<(std::ostream& stream, const RecordId& id) {
return stream << "RecordId(" << id.toString() << ')';
}
inline std::ostream& operator<<(std::ostream& stream, const boost::optional<RecordId>& id) {
return stream << "RecordId(" << (id ? id->toString() : 0) << ')';
}
} // namespace mongo
|